Generation of Blood Cells from Human Ips Cells in Vitro through the Hematopoietic Progenitors Concentrated within the Unique Structures, Ips-Sac.

Abstract

Human embryonic stem cells (hESCs) are proposed as an alternative source for transfusion therapy or studies of hematopoiesis. We have recently established an in vitro culture system whereby hESCs can be differentiated into hematopoietic progenitors within the ‘unique sac-like structures’ (ES-sacs), that are able to produce megakaryocytes and platelets (Takayama et al., Blood , 111, 5298–306, 2008). However there is a little concern that repetitive transfusion with same human ESC-derived platelets may induce immunological rejection against transfused platelets expressing allogenic HLA. Meanwhile, induced pluripotent stem (iPS) cells established from donor with identical HLA are well known as a potential and given source on platelet transfusion devoid of rejection. To examine if human iPS cells could generate platelets as well as from hESCs, we utilized 3 different human iPS cell lines; two were induced by transduction of 4 genes (Oct3/4, Klf4, Sox2, and c-Myc) in adult dermal fibroblasts, and one was by 3 genes without c-Myc. Sac-like structures (iPS-sac), inducible from 3 iPS cell lines, concentrated hematopoietic progenitors that expressed early hemato-endothelial markers, such as CD34, CD31, CD41a (integrin αIIb) and CD45. These progenitors were able to form hematopoietic colonies in semi-solid culture and differentiate into several blood cells including leukocytes, erythrocytes or platelets. Of these, obtained platelets responded to agonist stimulation, in which the function was as much as human ESC-derived platelets, as evidenced by PAC-1 binding with activated αIIbβ3 integrin or full spreading onto fibrinogen. These results collectively indicated that human dermal fibroblasts could generate functional and mature hematopoietic cells through the reprogramming process and this method may be useful for basic studies of hematopoietic disorders and clinical therapy in the future.